U.S. patent application number 12/398910 was filed with the patent office on 2009-09-10 for lcd display and electronic device.
This patent application is currently assigned to TPO Displays Corp.. Invention is credited to Naoki Sumi, Keitaro Yamashita, Masahiro Yoshiga.
Application Number | 20090225096 12/398910 |
Document ID | / |
Family ID | 41053132 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090225096 |
Kind Code |
A1 |
Yoshiga; Masahiro ; et
al. |
September 10, 2009 |
LCD DISPLAY AND ELECTRONIC DEVICE
Abstract
Disclosed is an LCD display utilizing a frame memory and a
lookup table for pixel overdrive. A plurality of pixels is arranged
in an array corresponding to the gate lines and the source lines.
The frame memory is a memory formed by at least one storage
capacitor and at least one thin film transistor in each pixel.
Moreover, a compression unit and a decompression unit are coupled
with the frame memory. The compression unit outputs compressed
gradation data of the present image. The decompression unit outputs
decompressed gradation data of the former image.
Inventors: |
Yoshiga; Masahiro; (Nishiku,
JP) ; Sumi; Naoki; (Nishiku, JP) ; Yamashita;
Keitaro; (Nishiku, JP) |
Correspondence
Address: |
LOWE HAUPTMAN HAM & BERNER, LLP
1700 DIAGONAL ROAD, SUITE 300
ALEXANDRIA
VA
22314
US
|
Assignee: |
TPO Displays Corp.
Kobe-shi
JP
|
Family ID: |
41053132 |
Appl. No.: |
12/398910 |
Filed: |
March 5, 2009 |
Current U.S.
Class: |
345/545 ;
345/87 |
Current CPC
Class: |
G09G 3/3648 20130101;
G09G 2340/16 20130101; G09G 2320/0252 20130101; G09G 2300/0842
20130101; G09G 2320/0285 20130101; G09G 2320/0261 20130101 |
Class at
Publication: |
345/545 ;
345/87 |
International
Class: |
G09G 5/36 20060101
G09G005/36 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2008 |
JP |
2008-054253 |
Claims
1. An LCD display, comprising: a plurality of pixels, arranging in
an array corresponding to gate lines and source lines; a frame
memory, forming by at least one storage capacitor and at least one
thin film transistor in each pixel; and a compression unit and a
decompression unit, coupling with the frame memory, wherein the
compression unit outputs compressed gradation data of a present
image and the decompression unit outputs decompressed gradation
data of a former image.
2. The LCD display according to claim 1, wherein one end of the at
least one storage capacitor is coupled to a drain of the thin film
transistor, the other end thereof is coupled to one of the gate
lines, a source of the at least one thin film transistor is coupled
to one of the source lines, and a gate thereof is coupled to a
read/write line.
3. The LCD display according to claim 1, wherein the at least one
storage capacitor and the at least one thin film transistor are
formed with the same lithography process of a thin film transistor
for driving each of the pixels.
4. The LCD display according to claim 1, wherein a compression
ratio of the compressed data is between 1/4-1/10.
5. An electronic device, comprising the LCD display of claim 1,
wherein the electronic device is a cellular phone, a digital
camera, a Personal Digital Assistant, a media display in car, a
digital frame and a portable DVD player.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Application claims priority of Japanese Patent
Application No. 2008-054253, filed on Mar. 5, 2008, the entirety of
which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to a liquid crystal
display (LCD display), and more particularly to a frame memory of
pixel overdrive in a liquid crystal display (LCD display).
[0004] 2. Description of Prior Art
[0005] Recently, LCD displays are utilized not only for
manufacturing computer monitors or LCD TV, but also for
manufacturing other products, such as cellular phones, digital
cameras, Personal Digital Assistants (PDAs), and various portable
electronic devices. However, because the LCD display response time
cannot be sufficiently short, display of residual image remains a
problem. Therefore, a pixel overdrive can be utilized to drive the
LCD display so that the LCD display can have a shorter response
time. In showing fast motion images thereupon by the pixel
overdrive, a higher voltage is provided to the liquid crystals than
would be generally provided from the gradation data of the former
image to the gradation data of the present image when the changing
direction is positive. Conversely, a lower voltage is provided to
the liquid crystals than would be generally provided from the
gradation data of the former image to the gradation data of the
present image when the changing direction is negative. Accordingly,
the response time of the LCD display is shortened and the quality
of the motion images is improved.
[0006] Refer to FIG. 3, which depicts a diagram of a pixel
overdrive arrangement. The abscissa expresses the frame time (frame
number) when moving from dark gradation to bright gradation, and
the ordinate expresses the gradation levels of the LCD display. For
example, in a 60 Hz driving circuit of an LCD display, one frame
represents 1/60.sup.th of a second, i.e. a period of 16.7
milliseconds. For reaching the gradation of the target 1, the
signal voltage of the target 1 has to be applied constantly for 5
frames. With the pixel overdrive, the gradation of the target 1 can
be reached in 1 frame by applying the signal voltage of OD1
(OVERDRIVE 1). Thereafter, the signal voltage is dropped to the
signal voltage of the target 1, and the response time of the LCD
display is shortened. Similarly, for reaching the gradation of the
target 2, the signal voltage of the target 2 has to be applied
constantly for 4 frames. With the pixel overdrive, the gradation of
the target 2 can be reached in 1 frame by applying the signal
voltage of OD2 (OVERDRIVE 2).
[0007] Refer to FIG. 4, which depicts a block diagram of a pixel
overdrive circuit according to a prior art. A general pixel
overdrive circuit is required to have an independent frame memory
42 to store the look up table 43 and the target gradation data for
outputting the proper gradation data to the LCD module (pixel)
41.
[0008] However, in the above-mentioned prior art, the independent
frame memory 42 cannot be eliminated in such pixel overdrive
circuit, a higher production cost will be a concern.
SUMMARY OF THE INVENTION
[0009] An objective of the present invention is to provide a lower
production cost LCD display for pixel overdrive without an
independent frame memory.
[0010] For accomplishing the aforesaid objective of the present
invention, a frame memory formed as a memory for pixel overdrive in
each pixel is utilized to eliminate an independent frame memory,
therefore, a lower production cost LCD display for a pixel
overdrive can be provided.
[0011] (1) The LCD display of the present invention utilizes a
frame memory and a lookup table for pixel overdrive. The LCD
display comprises a plurality of pixels arranged in an array
corresponding to the gate lines and the source lines. The frame
memory is a memory formed by at least one storage capacitor and at
least one thin film transistor in each pixel. A compression unit
and a decompression unit are coupled with the frame memory, wherein
the compression unit outputs compressed gradation data of the
present image and the decompression unit outputs decompressed
gradation data of the former image.
[0012] (2) The LCD display as described in (1), one end of the at
least one storage capacitor is coupled to a drain of the thin film
transistor, the other end thereof is coupled to one of the gate
lines, a source of the at least one thin film transistor is coupled
to one of the source lines, and a gate thereof is coupled to a
read/write line.
[0013] (3) The LCD display as described in (1) or (2), the at least
one storage capacitor and the at least one thin film transistor are
formed with the same lithography process of a thin film transistor
for driving each of the pixels.
[0014] (4) The LCD display as described in (1).about.(3), a
compression ratio of the compressed data is between 1/4 -1/10.
[0015] (5) An electronic device comprises the LCD display as
described in (1).about.(4). The electronic device is a cellular
phone, a digital camera, a Personal Digital Assistant, a media
display in car, a digital frame or a portable DVD player.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 depicts an embodiment of a frame memory according to
the present invention;
[0017] FIG. 2 depicts a diagram of a pixel overdrive circuit
according to the present invention;
[0018] FIG. 3 depicts a diagram of a pixel overdrive
arrangement;
[0019] FIG. 4 depicts a block diagram of a pixel overdrive circuit
according to a prior art.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Refer to FIG. 1, which depicts an embodiment of a frame
memory according to an embodiment of the present invention. As
shown in FIG. 1, each pixel is surrounded by gate lines GLn-1, GLn,
and source lines SL. Besides, each pixel comprises a frame memory
212 which is coupled with a read/write line R/WL. Generally, the
pixel unit 214 comprises a thin film transistor 11, a storage
capacitor Cs and a liquid crystal Clc. The storage capacitor Cs and
the liquid crystal Clc are coupled to the thin film transistor 11.
Inside each pixel area, the frame memory 212 comprises a storage
capacitor Cm and a thin film transistor 12. The storage capacitor
Cm stores gradation data of an image. The thin film transistor 12
is utilized to select read/write line R/WL. One end of the storage
capacitor Cm is coupled to the drain of the thin film transistor
12, and the other end is coupled to the gate line GLn-1. The source
of the thin film transistor 12 is coupled to the source line SL,
and the gate of the thin film transistor 12 is coupled to the
read/write line R/WL.
[0021] Refer to FIG. 2, which depicts a diagram of a pixel
overdrive circuit according to an embodiment of the present
invention. As shown in FIG. 2, the frame memory 212 is formed
therewithin a pixel of an LCD module 21. A compression unit 22 and
a decompression unit 23 are coupled with the frame memory 212. The
compression unit 22 outputs compressed gradation data of the
present image. The decompression unit 23 outputs decompressed
gradation data of the former image.
[0022] As shown in FIG. 2, the gradation data of the present image
is compressed as inputted data by the compression unit 22 and
inputted into the frame memory 212. At present, the read/write line
R/WL is selected and the foregoing compressed inputted data is
written into the storage capacitor Cm. Initially, the read/write
line R/WL is selected during the execution of the pixel overdrive.
The gradation data of the former image which is stored in the frame
memory 212 is read and the decompression unit 23 decompresses the
gradation data of the former image. The decompressed gradation data
of the former image is then inputted into the look up table 24 for
comparison process with the gradation data of the present image.
With the aforesaid comparison, the overdrive voltage is determined
and inputted into the pixel 214. If the gradation data of the
former image and the gradation data of the present image are the
same, the pixel overdrive will not be processed. If the gradation
data of the former image and the gradation data of the present
image are different, then the pixel overdrive will be processed.
Furthermore, as the read line is closed, the gate line is selected
and the overdrive voltage is applied to the pixel. Finally, as the
gate line is closed, the write line is opened and the gradation
data of the present image is stored in the frame memory 212.
[0023] The frame memory of the present invention can be utilized
not only in the foregoing structure, but also SRAM or other types
of memories to realize the same achievement. Moreover, the same
objective can be realized by utilizing at least two thin film
transistors and at least two storage capacitors in combination.
[0024] A compression ratio of the compression unit of the present
invention can be between 1/4-1/10and there is no particular
restriction to the decompression unit.
[0025] Because the frame memory comprises the storage capacitor and
the thin film transistor, the frame memory can be formed with the
same lithography process of a thin film transistor for driving the
pixel. Accordingly, the manufacture cost is lower than the prior
arts utilizing an independent frame memory.
[0026] The look up table of the LCD display stores gradation data
for pixel overdrive according to the present invention. The
gradation data for pixel overdrive is obtained by experiment in
advance. Alternatively, two look up tables can also be illustrated.
One is for determining the overdrive voltage and the other is for
determining predictive voltage.
[0027] The LCD display can also be applied in an electronic device,
such as a cellular phone, a digital camera, a Personal Digital
Assistant, a media display in car, a digital frame and a portable
DVD player.
[0028] As is understood by a person skilled in the art, the
foregoing preferred embodiments of the present invention are
illustrative rather than limiting of the present invention. It is
intended that they cover various modifications and similar
arrangements be included within the spirit and scope of the
appended claims, the scope of which should be accorded the broadest
interpretation so as to encompass all such modifications and
similar structure.
* * * * *